About Dolphins

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What are dolphins like?

Dolphins are a type of mammal called cetaceans (se-tay-shuns). Cetacean species worldwide include dolphins, whales and porpoises. Forty four cetaceans have been observed in Australian waters. Thirteen of these are dolphin species.

South Australia is home to the common bottlenose dolphin, the Indo-Pacific bottlenose dolphin and the short-beaked common dolphin. The Indo-Pacific bottlenose dolphin is the resident species in the Adelaide Dolphin Sanctuary.

Dolphins are shaped like fish, but have streamlined hairless bodies rather than scales. Their skin consists of several layers with a thin outer layer (like rice paper), a layer of blubber and a tough inner layer of fibres.

The tail flukes of cetaceans are horizontal rather than the vertical ones of fish. Their flippers, flukes and dorsal fin are used to balance, steer and move them through the water. Dolphins are strong swimmers, travelling about 5-10 km per hour, reaching speeds of 30 km per hour.

Breeding

Dolphins become sexually mature at different ages, depending on species and gender. Sexual maturity has been estimated at, on average, between 9 to 14 years. bottlenose dolphins breed all year round, and although calves may be born throughout the year, the majority are born in spring and summer after a gestation period of about 12 months. Calves are about 50-70% of the mother's length when born. Females calve at 3-6 year intervals, although this can vary.

Calves can suckle milk from their mothers until around 18 months of age, but because teeth develop in the first few months they can begin eating fish from about six months of age. Calves can stay with their mothers for about 4 to 5 years, when female calves may continue to live near their mother, whilst males may leave for other groups.

Dolphin life spans

Dolphin life spans vary between species, with expectancies estimated to range from 40-50 years for bottlenose, and 15-25 years for common dolphins.

Tooth analysis is widely recognised as an accurate indicator of a dolphin's age. The technique counts the growth layers in teeth and relates them to time taken to grow.

Their senses

Dolphins have excellent eyesight both in and out of the water. They are sensitive to touch on their skin, have taste buds, but have a limited sense of smell. Echolocation, a form of sound waves helps them to map out their surroundings, navigate and hunt.

See Dolphins of South Australia brochure (100Kb PDF)

Further information about dolphins

Frequently Asked Questions….and answers
http://www.faqs.org/faqs/animals/dolphin-faq/part01/

Dolphin Information
http://www.factmonster.com/ce6/sci/A0857792.html

Sarasota Dolphin Research Program
http://www.sarasotadolphin.org/

Australian Museum on line
http://www.amonline.net.au/mammals/resources/cetacean_faq.htm#how_many